So much of the pleasure of motorcycling is auditory: the intake growl of a GSX-R, the thump and rumble of a Big Twin, even the quiet whir of an electric motorcycle, where the loudest noise is the sound of the chain moving around its sprockets. When Motorcyclist commissioned Grado Labs to build a custom pair of headphones out of Harley-Davidson Street 750 pistons, we hoped the collaboration would highlight the association between high-fidelity audio (the hardware of sound) and motorcycles (the sound of hardware).

Grado’s history is a very American story. In 1953, Joseph Grado, a watchmaker at Tiffany and Co., started building phono cartridges at his kitchen table in Brooklyn, New York. Three generations in and Grado is still a family-run business operating out of the same factory that Joseph opened above his father’s grocery store in 1955. In addition to its phono cartridges, Grado’s signature open-back headphones have cemented its legacy in the high-end audio world and beyond. Every product that bears the family name retains Grado’s original philosophy of handcrafted quality.

“All we are concerned about is the sound,” says president and CEO John Grado, who released the original headphone line in 1990. “We’ve built a reputation around what is known as ‘the Grado sound.’”

To the uninitiated, Grado headphones, which often use handmade wooden enclosures, look decidedly old-school. And in certain ways, they are. Though the headphones have a low enough impedance (32 ohms) to be driven by an iPhone or iPod, they really demand to be powered by a headphone amp, or home receiver. That means you’ll be less likely to use them at the airport or on the subway. But that’s as it should be. These ’phones are for sitting down, closing your eyes, and simply listening. Like shutting out life’s distractions with the flip of a dark visor, putting on a pair of high-end headphones tunes out the world beyond the music.

As a complex of mechanical elements, the motorcycle itself is a source of fascination and attraction: the subtle etched lines of a billet footpeg, the satisfying click of a detented damping adjuster beneath a screwdriver, the snappy return of a properly adjusted throttle. The Grado headphones offer a tactile pleasure tantamount to the most beautiful motorcycle part. Lifting the headphones by their piston enclosures and leather headband is a reminder of the relationship between the moto and the audio worlds. Each housing weighs 8.5 ounces, a mass that Grado says helps shield the driver from outside resonances. The heft of the headphones is pleasing in the hand but sufficiently lightweight when worn.

For Grado, the biggest challenge of turning pistons into a pair of headphones was figuring out how to properly vent air to enable the driver to move freely. Rather than milling out a simple circle from the center of the piston, Grado removed a bar and shield-shaped vent, then added an internal vented cocobolo structure to surround the 50 mm dynamic transducers derived from its GS2000e headphones. Since airflow is the name of the game, Grado—as is its typical practice—used large foam earpieces to prevent a seal around the ear. In place of piston rings, there are beautiful cocobolo inlays. Junction blocks made of the same wood connect the enclosures to the sumptuous leather headband borrowed from the company’s top-line PS2000e headphones. Heavyweight 12-conductor cables as thick as brake lines hang from the enclosures and tether the listener to the audio source.

The purity of the tones and the generous ­soundstage convey the headphones’ built-right, only-the-essentials design.

On Colter Wall’s “Motorcycle,” slight fret buzz from the finger-picked guitar is palpable, displaying great clarity and detail without being so precise as to sound sterile. Thanks to the open-back design and the freely moving driver, the listener can hear the echo of Wall’s voice in the recording studio, conveying a capacious soundstage. It’s as though the listener’s room is transformed into a small-town bandstand at a sweltering Fourth of July concert. While some closed-back headphones can seem to hem in the listener, the Grados offer a far less claustrophobic experience. Peer into the generous ear cups, past the drivers, and the other side of the room is visible. That openness is evident in the sound.

These Grado headphones aren’t high-tech in the way the general population defines it—at least not when it comes to personal audio. There’s no noise-canceling circuitry, no wireless connectivity, no attempt at achieving absolute portability. But the perception of what’s on the bleeding edge of technological advancement doesn’t have to be the only metric of judging value.

A motorcycle’s merit, if determined by measurable performance, is an ever-moving target. As technology advances, a rider’s notion of what’s good moves on with it. In the hi-fi world, on the other hand, the ultimate metric of determining value is unchanging: the human ear. It’s not that high-fidelity technology hasn’t adapted at a commensurate rate to motoring technology, but what sounded good decades ago can sound just as good today. Excellence, as the Grados exemplify, is not contingent on the newest technical innovation or our perception of what’s high-tech.

It’s not a bad lens through which to judge a motorcycle. For some riders, the best Harley may not be the “best” motorcycle in the lineup. And next to a Ducati Panigale V4, a Kawasaki H2R, or a BMW HP4 Race, Harleys don’t match up. Judged by performance and technology metrics—acceleration, braking, handling—a Harley is inferior, plain and simple. But what this pair of Grado headphones taught me, and what Harley devotees have known all along, is that judging a motorcycle by a constant human metric—not something as fickle as technology—affirms the thing doing the judging, not the thing being judged.

Maybe you think that’s a cop out. “Let’s call a spade a spade,” you may be thinking. After all, Harley-Davidson doesn’t exist in a vacuum. Except for when it does. Some riders couldn’t care less about what’s outside the Harley vacuum. For them, Harleys hit all the right notes. Harleys are what move them.

In honor of 115 years of moving people, we thought it would be fitting to present Harley with the Grado headphones as our contribution to the museum. The pistons are returning home to Milwaukee, but they’re bringing a piece of Brooklyn with them.

However, even if you transform them into a pair of headphones, they don’t stop being Harley pistons. It’s just what they are. It’s the same with Harley riders themselves. For that crowd, the sound of a Harley is as profound as the second movement of Beethoven’s seventh symphony, and that’s all that matters.

And when that symphony is heard through the right pair of headphones, it’s downright transcendent.